Thorp Air Command - T18.net

Hello all,
This one is a head scratcher, awhile back I experienced low oil pressure at both cruise and idle on my o290g, at cruise I normally had 55 psi and 45 at idle, but the other day while flying I noticed oil pressure at 35psi cruise and 10-15 psi at idle, so I checked for any restrictions and found none (both oil screens) inspected oil pressure relief, cleaned and reinstalled and no change so I decided to add 1 washer behind oil pressure spring and pressure went up to 55 psi at idle and 65 at cruise, awsome right? Well I also decided now would be a good time to install a Airwolf remote oil filter system, which i did, changed oil and fired her up, now oil pressure is down to 40 psi at idle 45 psi at full throttle, "what the heck" so I added a second washer and pressure went up to 45 idle to 50 psi at full throttle, so I added a 3rd washer and now 55 at idle and 59 at full throttle, what gives? by adding a remote oil system would that have that much effect on Oil pressure? Even at 59 psi I'm still below minimum oil pressure according to the book, not sure why i experienced low oil pressure initially, the only thing i can relate it to was that the plane sat for two and a half months prior to to the oil problem, any ideas would be great, thanks....Ira

Is your gauge a direct read or a sender type unit ?

RB

Sender type, my next course of action is to confirm oil pressure with direct gauge

YOU GO GIRL !!

RB
BOOM , CHICKY BOOM

That's what I would do. Those are way defendant on a good ground, which can be hard to keep.
Cubes

Good morning, yesterday I installed a mechanical oil sender and it was within 1lb of my unit, I'll keep looking.

Stop flying it. Pull the oil pump gears.

_________________
http://www.dixiefriedfabrication.com/

Has AD 96-09-10 been complied with ? Replacement of oil pump impeller gears . Should be a log entry in the engine log ? Also two piece oil pump body should be replaced while you are in there looking for dead canaries in the mine shaft .

RB

It could be that the oil pump is eating itself up or a bearing(s) are getting excessive clearance causing the oil pressure to drop. What contradicts that is if the oil pump is not putting out enough volume, the oil pressure relief valve should be closed at all times.

The relief valve bypasses extra oil flow. If you don't have enough oil flow it should be closed. If it is closed, putting more washers under it really shouldn't increase the pressure as closed is closed. Looks like more washers is increasing pressure. If adding more washers did not increase pressure, that would show lack of adequate oil volume/pressure supply from pump.

If you don't already, maybe an oil analysis would help to see if more metal than normal. If you have not been doing analysis, it won't be as accurate, but would probably still show abnormal metal in oil anyway.

Almost seems as if it could be a problem with the oil pressure relief not sealing well.

_________________
Bernie Fried
N18XS

You may disconnect the new filter system and see what you have. This may not be the fix, just trouble shooting the problem. If this brings back things to normal you have one of two issues. The engin not producing enough pressure / volume or an issue with the filter assembly / installation.
Phil
118BC

Guys,

Previously I had a Stinson 108-3 and a few of the Stinson guys tried the AirWolf filter set up and also experienced low oil pressure. The Franklin engines did not have a filter system and the scarcity of parts was driving us to look at doing anything to extend the life of our engines. There was a lot of discussion about this with Airwolf and I believe they did not resolve the issue. I went with a system made by ADC and had no issues with my 165 hp Frankiln.

Regards,

Jim

Try this. Put in 60wt oil. If this does fix the problem you have a clearance problem in the bearings or the oil pump housing. I had an issue with my o290 in my first t-18. After pulling a low cylinder off I had found a internal crack in the case and was letting the oil bypass thru it.